Genotoxic effects of white fluorescent light on human lymphocytes in vitro

Abstract

Sources of light beams such as white fluorescent light, are present in our daily life to meet the needs of life in the modern world. This study was conducted with the objective of determining the possible genotoxic, cytotoxic and aneugenic effects caused by this agent in different stages of the cell cycle (G0/early G1, S, and late G2), using different cytogenetic parameters (sister chromatid exchanges––SCE, chromosome aberrations––CA, and detection of aneugenic effects) in lymphocytes from temporary cultures of human peripheral blood. WFL showed a genotoxic effect in vitro, expressed by an increase in the frequency of SCE's, regardless of the cell cycle stage. However, no increase in the frequency of CAs was observed. In addition, disturbances in cell cycle kinetics and chromosomal segregation were also observed. Taken together, such data may contribute to a better understanding and a different management in the use of phototherapy for some pathological conditions.

Introduction

In addition to sunlight, light produced by other artificial sources, such as white fluorescent light, ultra-violet and solar lamps, is present in our daily life to meet the needs of the modern world (leisure, work and the treatment of certain pathologic conditions). The pioneering works carried out with non-ionizing radiation, as the one produced by fluorescent light, have already demonstrated that this kind of radiation has a mutagenic effect on bacteria and that this effect becomes more pronounced whenever the wave length comes close to that of ultra-violet and blue light [1], [2]. More recent studies using white fluorescent light have shown that this agent induces mutations in bacteria which are similar to those produced by the sun, a well-known carcinogen [3].

A number of other studies performed in the seventies also showed deleterious effects (mutagenicity and toxicity) caused by white fluorescent light in fibroblast cultures of mammalian and human cells [4]. However, the analysis of sister chromatid exchanges (SCE's) in individuals exposed in vivo to fluorescent light showed discordant results, as there was sometimes an increase in the frequency of SCE's and others no change in this parameter at all [5], [6]. In spite of the discordant data, more recent studies tend to confirm the mutagenic effect of white fluorescent light in cell systems of mammals [7], [8].

Based on the exposé above, we can see that white fluorescent light is considered by several authors as a mutagenic agent in prokaryotes and mammalian cells, however, the amount of updated information on the possible effects of fluorescent light is small, and available studies in the literature are scarce. Thus, the present work had the objective of evaluating and reaching a better understanding of the mutagenic and clastogenic action of this light source on the DNA of peripheral blood leukocytes exposed in vitro. We further aimed at identifying possible alterations in the mitotic index (MI) and in the cell cycle kinetics as a result of the exposure of these cells to WFL, in different stages of the cell cycle and for distinct times of exposure.